Theorem tpid2 4774

Description: One of the three elements of an unordered triple. (Contributed by NM, 7-Apr-1994.) (Proof shortened by Andrew Salmon, 29-Jun-2011.)

Hypothesis

Ref	Expression
tpid2.1	⊢ 𝐵 ∈ V

Assertion

Ref	Expression
tpid2	⊢ 𝐵 ∈ {𝐴, 𝐵, 𝐶}

Proof of Theorem tpid2

Step	Hyp	Ref	Expression
1		eqid 2733	. . 3 ⊢ 𝐵 = 𝐵
2	1	3mix2i 1335	. 2 ⊢ (𝐵 = 𝐴 ∨ 𝐵 = 𝐵 ∨ 𝐵 = 𝐶)
3		tpid2.1	. . 3 ⊢ 𝐵 ∈ V
4	3	eltp 4692	. 2 ⊢ (𝐵 ∈ {𝐴, 𝐵, 𝐶} ↔ (𝐵 = 𝐴 ∨ 𝐵 = 𝐵 ∨ 𝐵 = 𝐶))
5	2, 4	mpbir 230	1 ⊢ 𝐵 ∈ {𝐴, 𝐵, 𝐶}

Syntax hints:   ∨ w3o 1087   = wceq 1542   ∈ wcel 2107  Vcvv 3475  {ctp 4632

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-ext 2704

This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-3or 1089  df-tru 1545  df-ex 1783  df-sb 2069  df-clab 2711  df-cleq 2725  df-clel 2811  df-v 3477  df-un 3953  df-sn 4629  df-pr 4631  df-tp 4633

This theorem is referenced by:  wrdl3s3  14910  wwlks2onv  29197  elwwlks2ons3im  29198  umgrwwlks2on  29201  s3rn  32100  cyc3evpm  32297  sgnsf  32309  sgncl  33526  signsw0glem  33553  signsw0g  33556  signswmnd  33557  signswrid  33558  prodfzo03  33604  circlevma  33643  circlemethhgt  33644  hgt750lemg  33655  hgt750lemb  33657  hgt750lema  33658  hgt750leme  33659  tgoldbachgtde  33661  tgoldbachgt  33664  kur14lem7  34192  brtpid2  34680  rabren3dioph  41539  oenord1ex  42051  oenord1  42052  fourierdlem102  44911  fourierdlem114  44923  etransclem48  44985